Can Rhesus Monkeys Recognize Their Own Reflection?

By Emily
Photo credits: Mor

Photo credits: Mor

Have you ever wondered why your pet doesn’t strike a pose when in front of a mirror? Well, that’s because most animals cannot recognize themselves in a mirror! Recent testing and studies conducted at the University of Wisconsin-Madison have shown that new head implants are able to trigger self-awareness, or the ability to understand that one exists as an individual, in rhesus monkeys. As only certain species, such as humans, some orangutans and chimpanzees, are self-aware, it is completely amazing that this technology has been discovered.

The head implant, which is made of acrylic blocks that attach to the monkey’s hair-thin electrodes, allowed it to pose and “check itself out” in front of a mirror. Recognizing one self in a mirror is believed to be a sign of self-awareness, and the monkey performed several self-directed behaviors while exposed to the mirror. It was hypothesized that the implant allowed the monkey to surmount its gaze aversion inhibition or lack of interest and actually examine itself in the mirror. Before the head implant was inserted, the monkey would try to socially interact with its reflection. He would touch and attempt to communicate with its image in the mirror, even after long exposure and much training.

The mark test, which is the standard test for self-awareness, is quite controversial but is commonly used to test self-awareness in different species. This test includes applying marks to the animal’s face while anesthetized, so that when the monkey wakes it will either touch the marks while in front of the mirror, or it will not. If the animal touches the marks, then it is said to have passed the test. Rhesus monkeys have persisted to fail this test and because of this, are not considered self-aware. However, results from this particular experiment show that the monkeys are able to recognize themselves in front of the mirror with the implant and have some form of self-awareness.

During the experiment, the monkey would move in front of the mirror and would even pick up the mirror and angle it, while it groomed the area around the implant. He would even smell and lick his fingers, which indicated that he understood the area being groomed was his own. The monkey did not attempt to groom his reflection or socialize with the image in the mirror, which is another indicator that he was self-aware.

The experiment is extremely interesting and has revealed much information about self-awareness in monkeys. Although monkeys have failed the mark test, they demonstrated some self-awareness when wearing the head implant. What other animals are self-aware? How have researchers made this discovery?

  • Emilio

    Great post Emily, I was somewhat aware that animals couldn’t recognize themselves in a mirror. From a less scientifically based standpoint, I’ve seen videos and have had pets who will see themselves in a mirror and claw at the mirror, hiss, and even run away from the mirror in what seems to be fear. Another example is a dog chasing its own tail. I was under the impression that humans were the only species who could recognize themselves in a mirror, and this seems to still stand. After all, the rhesus monkeys only show self-awareness with a head implant, not on their own, perhaps the only way to know for sure is to not use the implant and test the monkeys without it.


  • Eva

    This is a very interesting topic Emily! I did a little more research and foud that only humans, orangatangs and chimpanzees are the only animals that are able to achieve reflection recognition. As you mentioned, the mark test is also a very popular test on self-awareness. However, many more animals are able to pass this test. Scientists who conducted the mark test once thought that only humans could pass the test,but chimpanzees were soon able to pass it as well, followed then by dolphins and elephants that were able to pass the test. Overall if find both tests and the whole topic very interesting. But I wonder if scientists would be able to somehow unify the marking test and the mirror reflection test to see which animals truly are self-aware?

  • Ali Syed

    Great post Emily, as it turns out, the only other primate to recognize itself in a mirror is the Chimpanzee, scientifically known as “Pan Troglodytes”. Chimpanzees are commonly found in the Middle West region of Africa.Chimpanzees are our closest living relatives, sharing more than 98% of our genetic code. Chimpanzees live in social societies and can adapt themselves to African rain forests. Although they normally walk on all four legs (unusually on knuckles) chimpanzees can stand and walk upright. By swinging from branch to branch they can also move quite efficiently in the trees, where they do most of their eating. Chimpanzees usually sleep in the trees as well; setting up leaves to resemble beds. Chimps are generally omnivores. Chimpanzees are one of the only animal species that employ tools. They carve and use sticks to retrieve insects from their nests or dig grubs out of logs. They also use stones to smash open nuts and use leaves as sponges to soak up drinking water. Chimpanzees have also shown signs of compassion, empathy and courtesy/respect towards other species. Chimpanzees can even be taught to use sign language. Females can give birth at any time of year. Usually, an individual infant clings to its mother’s fur and later rides on her back until the age of two, similar to how babies are carried by humans. Females reach puberty at 13, while males are not adults until they are 16 years old. Chimpanzees can live up to 40 years old while they are in the wild, but can live up to 60 in captivity. Unfortunately they are considered endangered for that their habitats are being destroyed.

  • Taylor

    Your post was really fascinating Emily! After reading I researched what other animals that were being tested to see if they are “self-aware.” I found that elephants are also being tested for self-awareness. Researches conducted there experiment, by first starting with three large female asian elephants. Generally, elephants like to push things with there heads, so scientists were interested to see how the elephants would react to the platis mirror they used. They could not use glass, because it would’ve broken more quickly than the plastic. The first reaction to most animals, would be to explore the other side of the mirror. In this case, the elephants waved their trunks around and moved their heads in and out of the mirror view.In former studies, relatively small mirrors were used for the elephants, and they were kept out of the elephants reach. The primary goal, is to train the animals, to learn to investigate their own bodies, involuntarily. If you want to read the fascinating article, here’s the link: Enjoy!

  • Gurk

    That was a fascinating post Emily! Great job! That is really fascinating that the monkey did not know at first it was his reflection before the implant. The monkey’s behavior is just as the behavior of a baby going toward the mirror and hitting the mirror so he can play with his reflection. Sometimes the baby gets angry at the reflection copying his every move and starts to cry. The University of Wisconsin did a test with a mirror similar to this test but their style was to cover the mirror with a black plastic the monkey’s behavior began to change. First they gave a mirror to the monkey and he was fascinated at first but once they covered the mirror with black plastic the monkey’s fascination was gone. In this website they explain the whole process of this experiment.

  • Naseem

    Great comments, guys! I found another species in the Animal Kingdom that exhibited self-recognition through a similar scientific experiment, but it wasn’t a mammal. Birds have very different brain structures than mammals, and 75% of songbirds’ brains are made up of a complicated information processing system that works akin to the human cerebral cortex. Recently, the Magpie bird’s cognitive abilities were tested by psychologist Helmut Priot, and colleagues Ariane Schwartz and Onur Güntürkün. Just like the Rhesus monkeys, the German scientists subjected the magpie birds to a similar mark test, where a mark was strategically placed on the bird’s body for use with the mirror (no use of a head implant). I think this sort of test is what you were talking about, Eva. Researchers concluded that when the test subject interacted with the mark, i.e. scratching it, these birds were able to recognize they were the image in the mirror. This experiment proved to be very significant in findings regarding animal cognitive abilities. Non-mammalian species, as well as species without a neocortex, are now known to be able to engage in self-recognition behavior. The neocortex is a part of the cerebral cortex and is thought to be very vital in self-recognition abilities of mammals. It deals with higher cognitive processes like sensory perception, conscious thought, and language. The lack of neocortex in the Magpie bird shows that advanced cognitive skills may be able to develop without its presence. Do you think this new information could be harmful?

    How a Bird’s Brain Works:

  • Josh

    I am truly amazed that the world has invented and successfully tested technology that can completely change the way an animal thinks. People can now know if other species are able to recognize themselves. I have found that animals such as elephants and even dolphins can identify themselves. The magpie also shows self awareness. I had just thought of a small experiment that you can try at home if you own a household pet, dog, cat, bird, etc. Put the pet by the mirror and see what it does. The example (I did not film this). Then show the pet a sticker then place it on the animal and then see if the pet can realize it sees itself.,24791,26637&sugexp=ldymls&xhr=t&q=magpie+bird&cp=8&safe=active&wrapid=tljp1286975981139114&um=1&ie=UTF-8&source=og&sa=N&tab=wi&biw=1020&bih=583

  • Cartland

    It’s really a interesting post Emily! I did some researches after read your post, and I also find some interesting information. Elephants can also recognize themselves in a mirror, joining only humans, apes and dolphins as animals that possess this kind of self-awareness. Researches did experiences, they introducing three adult female Asian elephants to a mirror. The elephants are quite different from monkeys. In my opinion, elephants are much bigger and sluggish than monkeys, but they are also seems to interested in mirror. I guess that means that self-awareness of an animal is not relative with how the animals looks like. There’s something in their mind that control the self-awareness.


  • Jessica K.

    Facsinating post, Emily! I never knew that the majority of animals were not aware of their own existence, or “self-aware.” After conducting some additional research, I found that in addition to humans, orangutans, and chimpanzees, magpies, asian elephants, and bottlenose dophins are also able to recognize themselves when a mirror is placed in front of them. In addition, must humans fail the self-awareness test until they are about one and a half or two years old. As mentioned in the article, the most common way of testing an animal’s self-awareness is the “mirror test” or the “mark test.” If is determined if one passes by observing whether or not the animal acts amazed and surprised at the sight of it’s own reflection or if the animal will simply “check itself out.”


  • Sara

    Wow! I never knew that monkeys could recognize themselves in the mirror. This was a very interesting article, Emily! I actually researched if any other animals besides monkeys could see their reflection, and it actually turns out the dolphins can too as someone mentioned. But, it actually turns out that this experiment started in the New York Aquariam when scientists placed mirrors in a pool where two dolphins swim in. Then, the scientists marked the dolphins faces with black ink (non-toxic). The dolphins looked in the mirrors at the marks on their faces. Scientist Diana Reiss has concluded that this would mean the dolphins recognized themselves because they realized that there was something wrong with them. They say that dolphins have passed this test, because it is proved that they are easily trained and also because their brain size is larger than most animals. Other, animals will either ignore the image they see in the mirror or think that they are looking at a different animal or creature.

    If you want more information about this topic here is the website:,28277,109235,00.html

  • Liz Allen

    Hi Emily, this is PLoS checking in, we’re the publisher of the original article and we love what you wrote here. Helping more people understand science through blogging is a passion that we share with you. We’re so impressed, we are going to send you and Ms Baker a PLoS Blogs T-shirt (, so please email me back with your delivery address and sizes. Congratulations from all of us at PLoS.

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  • James

    Rally great post Emily! As you had mentioned in your blog how monkeys can become self-aware with the proper head implant. I had decided to look up more research on what other animals could recognize themselves in the mirror, and why they can. I had researched that elephants can recognize themselves in the mirror because elephants as well as monkeys also have this self-awareness ability. A scientist named Diana Reiss had said, “These abilities can only be achieved by animals with complex brains. Even though every animal’s brain is different. At first when Diana began to test the elephants they would swing their trunk over the big mirror. They had come to a discoing that if they used a smaller mirror maybe the elephant would see itself better. As a result the elephant had began to swing its trunk. This meant that the animal was seeing itself in the mirror. Really good post! I hope to see more post about animals self awareness!

  • Gunnar M

    Wow This is Great! I kind of knew that animals could not see themselves in the mirror. For example i have watched funny youtube videos where the animals would scratch the mirror or chase its tail. Come to realize i have only seen dogs and cats do that. I will post some clips of animals that do that but now knowing that Rhesus Monkeys do the same it really got me interested. But what really gets me into the topic is that just watching the animal try to interact with the mirror makes me think, How come it doesn’t recognize itself? But than i thought how would they be able to see themselves in the jungle or wild. I’m most definite that they don’t have mirrors in the wild so it”s as if they are encountering themselves for the first time but it can also be a dangerous thing. In one of the clips i found the cat pounced at the mirror which looked like it hurt do to the fact that it hit it’s head. But this could be a giant leap in animal science, Great Post Emily!


  • dawood

    Nice post Emily. In class we have been talking about animal behaviors for some time, and one particular behavior is insight. Only humans and a few other species of animals have insight. It allows them to solve problems that they haven’t faced before. Usually these animals would have complex, and sophistocated brains. After reading this article i sat down and thought for a while, and i came up with a question for everyone. Could having insight relate to animals being self aware?


    biology class

  • Alice

    This is so interesting, Emily! I have always been very fascinated with self-awareness and when I previously heard rumors that babies were in fact not self-aware, I was very interested in this topic. I did a little more research on self awareness in children and came across a very thought-provoking study that was performed at Emory University. Within this study, scientists ranked the level of self-awareness from zero to six, zero being the least self-aware. Young children, around the age of 2 to 3, were placed in front of a mirror with a yellow “Post-It” on their foreheads. Scientists asked the question, “when do children become aware of themselves as di?erentiated and unique entity in the world?”. These young children often showed very low levels of self-awareness, ranging from level 0 to 2. When looking into the mirror, these young children did not touch the post-it on their head, signaling that they didn’t understand the concept that they were looking at their reflection in the mirror. Studies are still being done on this very interesting and pressing topic.


  • Naseem

    Ali, this is the NOT CREDIBLE SOURCE Police! Though you’re not alone, you are another culprit that has absentmindedly used Wikipedia as a source for your comment!!! ‘Wiki’pedia is a ‘Wiki,’ meaning anyone on the internet can make an account and edit anything! This site isn’t always the best to use a source because you can read, believe, and then use false information, which is embarrassing! For you, I found two studies ( and ( on self awareness found in chimpanzees, and a page with Pan trogodytes, or chimpanzee facts (

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